Muscle fatigue and pain and their effects on central nervous activity

Dettagli del progetto

Costo totale:

Contributo UE:

Coordinato in:

Argomento (i):

Obiettivo

Muscle fatigue is a phenomenon of a great practical importance for all individuals in everyday experience, physically demanding occupations, and sport. The phenomenon should be particularly taken into account in patients with various types of disorders affecting the CNS and peripheral neuromuscular apparatus. Despite of importance of the phenomenon, little is yet known about many fine mechanisms contributing to pure muscle components and the means available to the CNS to compensate for its effect at least partly. Insufficiently investigated questions in the problem relate to possibility of interaction of the fatigue effects within a separate muscle and agonistic muscle groups.

The aim of the project is to study of these questions in animal and human experiments in accordance with the following tasks:

- To investigate mechanisms of fatigue development within a single muscle;to describe the time course of depression and restoration of contractility of non-active muscle fibres following fatiguing stimulation of the surrounding muscle tissue, as well as to describe lengthening and shortening trajectories under servo-control of external load during development of fatigue; to study changes in systemic blood pressure and in intramuscular pressure during fatiguing stimulation (experiments on anaesthetized cats);- To investigate fatigue-related changes in excitability of the spinal cord; to describe changes in the monosynaptic reflexes evoked by stimulation of the nerves to mm. gastrocnemius-soleus and posterior biceps-semitendinosus after fatiguing stimulation of gastrocnemius-soleus muscle; to study post-fatigue changes in the intensity of presynaptic inhibition and in various components of the stretch reflex; to investigate post-fatigue changes in focal potentials and neuronal activity in the projection zones of high-threshold muscle afferents (experiments on anaesthetized cats);- To study c-Fos expression and NO synthase (NOS) reactivity in the central nervous system following fatiguing muscle stimulation or long-lasting selective activation of low-threshold muscle afferents; to elucidate the terminal projections of Fos-immunoreactive and NOS-containing neurons by means of retrograde labelling with fluorophores; to study c-Fos expression and NOS activation in the brain and spinal cord neurons following chronic myositis (experiments on anaesthetized cats);- To visualize brain systems involved in perception of muscle fatigue effects by means of positron emission tomography; to compare post-fatigue maps of neuronal activity with those evoked by experimentally induced pain (intramuscular injections of hypertonic saline solution) and following long-lasting selective activation of muscle spindle afferents during muscle vibration (experiments on conscious healthy humans).

Pilot experiments in part of the studies are already in progress. The research teams have experience in conducting of the common investigations in the direction of the proposed project. The proposed investigations will provide new fundamental data that might be useful for developing new approaches to study muscle fatigue and related central processes.